Effect of sulfur passivation on the InP surface prior to plasma-enhanced chemical vapor deposition of SiN_x

The fabrication of Au/SiN_x/InP metal-insulator-semiconductor (MIS) diodes has been achieved by depositing a layer of SiN_x on the (NH₄)₂S_x-treated n-InP. The SiN_x layer was deposited at 200 °C using plasma-enhanced chemical vapor deposition (PECVD). The effect of passivation on the InP surface before and after annealing was evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements, and Auger electron spectroscopy (AES) analysis was used to investigate the depth profiles of several atoms. The results indicate that the SiN_x passivation layer exhibits good insulative characteristics. The annealing process causes distinct inter-diffusion in the SiN_x/InP interface and contributes to the decrease of the fixed charge density and minimum interface state density, which are 1.96 × 10¹² cm ^-2 and 7.41 × 10¹¹ cm^-2 eV^-1, respectively. A 256 × 1 InP/InGaAs/InP heterojunction photodiode, fabricated with sulfidation and SiN_x passivation layer, has good response uniformity.